Radiation sensitive material and method for forming pattern

ABSTRACT

A copolymer expressed by the following structural formula was obtained by loading adamantyl methacrylate monomer and t-butyl acrylate monomer by 1:1, then conducting polymerization, adding AIBN as a polymerization initiator, and then conducting precipitation purification with methanol. Then to the copolymer, triphenylsulfonium hexafluoroantimonate was added to prepare a cyclohexanone solution. This solution was applied to a wafer, and exposed to a KrF excimer stepper and developed. The threshold energy Eth was 50 mJ/cm&lt;SUP&gt;2&lt;/SUP&gt;. A 0.45 mum-wide L &amp; S was formed at 130 mJ/cm&lt;SUP&gt;2&lt;/SUP&gt;. The radiation sensitive material has good transparency and etching resistance, high sensitivity, and little peeling.

BACKGROUND OF THE INVENTION

The present invention relates to a radiation sensitive material and aprocess for forming a pattern using the same.

Recently, semiconductor integrated circuits have become more integratedand LSIs and VLSIs are practically available. Accompanying suchintegration, circuit patterns have become smaller in size, approachingsubmicron dimensions and even smaller. Formation of a pattern in asubmicron dimension essentially requires lithography. In lithography athin film resist is deposited on to a substrate to be processed, and isselectively exposed and developed to form a resist pattern. With thisresist pattern as a mask, dry etching is conducted and then the resistis removed to obtain a required pattern. As an exposure source forlithography, ultraviolet radiation was originally used, but as circuitpatterns approach submicron sizes, far ultraviolet radiation (e.g.electron beams, X rays, etc.) with short wavelengths, are used asexposure sources.

Especially for lithography using excimer lasers (248-nm wavelength KrFlaser and 193-nm wavelength ArF laser), resist materials having highresolution, high sensitivity and good dry-etching resistance arerequired.

Many conventionally developed resists are based on phenol resin andnovolak resin. These materials have aromatic rings and good dry etchingresistance, but they have poor transparency at KrF wavelength and aretotally opaque at ArF wavelength. Consequently they can not providepatterns sufficiently precise in submicron dimensions.

On the other hand, as a transparent resist for excimer beams, t-butylmethacrylate polymer is proposed, but this resist lacks dry etchingresistance.

As a countermeasure to this, the inventors have proposed a chemicalamplification type resist using alicyclic groups as a resist having dryetching resistance comparable with that of aromatic compounds and aretransparent at KrF and ArF wavelength. Here alicyclic groups areadamantane, norbornane, perhydroantracene, cyclohexane,tricyclo[5.2.1.0^(2,6)]decane etc., and adamantyl groups are suitable(see Japanese Patent Laid-Open Publication No. 39665/1992).

But the chemical amplification type resist of alicyclic copolymerincreases hydrophobicity and rigidity of the alicyclic group, whichgives dry etching resistance, increases its composition ratio.

At a composition ratio which gives dry etching resistance comparable tothat of phenol resin-based and novolak resin-based resists, e.g., above50 mol % of alicyclic unit, because of high hydrophobicity and rigidityof the resists, diffusion of protonic acid as a catalyst is hindered,which results in lower amplification, smaller amounts of carboxylic acidbeing generated, and lower solubility to a developer of an alkalineaqueous solution.

Furthermore, these resists lack adhesiveness, and, in addition, theirresist films are rigid because of inclusion of alicyclic groups. As aresult, strain caused to the resist films become larger, and the resistfilms have a greater tendency to peel off. Accordingly stable patterncharacteristics cannot be obtained. This is also a problem.

SUMMARY OF THE INVENTION

In view of these problems, an object of the present invention is toprovide a radiation sensitive material for an excimer laser lithography,having good transparency and etching resistance, is highly sensitive,has good adhesion and to provide a method for forming a circuit patternusing the radiation sensitive material.

Another object of the present invention is to provide a method forforming a pattern which can produce a protective film from even anon-phenol based polymer of low polarity, and which can have stablepattern characteristics.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer expressed by ageneral formula

(where Y represents alicyclic group; R₁ and R₂ represent CH₃ or H, andat least one of R₁ and R₂ is H; and R₃ represents alkyl group); and asubstance generating an acid by application of radiation.

In the above-described radiation sensitive material, it is preferablethat the copolymer includes, by 40-70 mol %, a unit structure includingalicyclic groups.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer including a unitstructure which is expressed by a general formula

(where R₁ represents CH₃ or H); and which generates an alkali solublegroup in the presence of methacrylic acid or acrylic acid, and an acid;and a substance generating an acid by application of radiation.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a terpolymer expressed by ageneral formula

(where Y represents alicyclic group;

-   Z represents —C(CH₃)₂R₄,-   R₁, R₂, and R₃ represent CH₃ or H; and R₄ represents alkyl group);    and a substance generating an acid by application of radiation.

Here groups which generate alkali soluble groups in the presence of acidare, an ester group, t-butyl group, tetrahydropyranyl group,α,α-dimethylbenzyl group, 3-oxocyclohexyl group, etc., and groups whichare released in the presence of protonic acid can be used. In view oftransparency with respect to excimer beams, groups without benzene ringsare suitable. Thus, t-butyl group, tetrahydropyranyl group,3-oxocyclohexyl group are more preferable.

In the above-described radiation sensitive material, it is preferablethat the copolymer includes the unit structure having carboxylic acid inthe range of 5-35 mol %.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer including a unitstructure which is expressed by a general formula

and which generates an alkali soluble group in the presence ofmethacrylic acid and an acid; and a substance generating an acid byapplication of radiation.

The above-described object is achieved by a radiation sensitive materialcomprising: a terpolymer expressed by a general formula

(where Y represents alicyclic group; and

-   Z represents —C(CH₃)₂R₃,-   R₁ and R₂ represent CH₃ or H; and R₃ represents alkyl group); and a    substance generating an acid by application of radiation.

Here groups which generate alkali soluble groups in the presence of acidare, as ester group, t-butyl group, tetrahydropyranyl group,a,a-dimethylbenzyl group, 3-oxocyclohexyl group, etc., and groups whichare released in the presence of protonic acid can be used. In view oftransparency with respect to excimer beams, groups without benzene ringsare suitable. Thus, t-butyl group, tetrahydropyranyl group,3-oxocyclohexyl group are more preferable.

In the above-described radiation sensitive material, it is preferablethat the copolymer includes the hydroxyethyl methacrylate by above 5 mol%.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer including a unitstructure expressed by

(where X₁ and X₂ represent —C(CH₃)₂R₁,

and R₁ represents alkyl group); and a unit structure generating analkali soluble group in the presence of an acid; and a substancegenerating acid by application of radiation.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer expressed by ageneral formula

(where X₁ and X₂ represent —C(CH₃)₂R₂,

Y represents alicyclic group; R₁ represent CH₃ or H; and R₂ representsalkyl group); and a substance generating an acid by application ofradiation.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer including a unitstructure expressed by

(where X₁ and X₂ represent —C(CH₃)₂R₁,

and R₁ represents alkyl group); and a unit structure generating analkali soluble group in the presence of an acid; and a substancegenerating an acid by application of radiation.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer expressed by ageneral formula

(where X₁ and X₂ represent —C(CH₃)₂R₂,

Y represents alicyclic group; R₁ represent CH₃ or H; and R₂ representsalkyl group); a substance generating an acid by application ofradiation.

The above-described object of the present invention is achieved by aradiation sensitive material comprising: a copolymer including a unitstructure expressed by a general formula

(where at least one of X and Y is a nitrile group) and a unit structuregenerating an alkali soluble group; and a substance generating an acidby application of radiation.

In the above-described radiation sensitive material, it is preferablethat the copolymer includes t-butyl groups.

In the above-described radiation sensitive material, it is preferablethat the copolymer includes alicyclic groups.

In the above-described radiation sensitive material, it is preferablethat the unit structure

(where at least one of X and Y is nitrile group) is acrylonitrile ormethacrylonitrile.

In the above-described radiation sensitive material, it is preferablethat the copolymer includes the acrylonitrile or methacrylonitrile by10-70 mol %.

The above-described object is achieved by a radiation sensitive materialcomprising a terpolymer expressed by a general formula

(where X represents H or CH₃;

-   R represents-   R₁ and R₂ represent H, R₃ represents-   R₁ represents CH₃, R₂ represents H, R₃ represents-   R₁ and R₂ represent CH₃, R₃ represents-    or-   R₁, R₂ and R₃ represent CH₃); and a substance generating an acid by    application of radiation.

The above-described object is achieved by a radiation sensitive materialcomprising a resist containing a hydrophilic group and a hydrophobiccompound.

It is preferred that the resist containing a hydrophilic group is acopolymer expressed by a general formula

(where X represents H or CH₃;

-   R represents-    and-   R₁ and R₂ represent H, R₃ represents-   R₁ represents CH₃, R₂ represents H, R₃ represents-   R₁ and R₂ represent CH₃, R₃ represents-    or-   R₁, R₂ and R₃ represent CH₃)

In the above-described radiation sensitive material, the resist containsvinylphenol, which contains hydrophilic groups, in the range of 50-70mol %.

In the above-described radiation sensitive material, the resistcontaining hydrophilic groups is a copolymer expressed by a generalformula

(where R represents

In the above-described radiation sensitive material, it is preferredthat the resist contains vinylphenol, which contains hydrophilic groups,in the range of 60-80 mol %.

In the above-described radiation sensitive material, it is preferredthat the hydrophobic compound is expressed by a general formula

In the above-described radiation sensitive material, it is preferredthat the hydrophobic compound is expressed by a general formula

(where R₁ and R₂ represent

or

-   R₁ represents-    R₂ represents

The above-described object of the present invention is achieved by aradiation sensitive material comprising a copolymer including itaconicanhydride which is expressed by

and a polymer as a unit structure generates an alkali soluble group inthe presence of an acid; and a substance generating an acid, uponapplication of radiation.

In the above-described radiation sensitive material, it is preferredthat the copolymer is expressed by a general formula

(where l, m and n represent 0-60 mol %, 10-95 mol %, 5-50 mol %respectively; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkyl group,C₁₋₄ substituted alkyl group, nitrile group, —(CH₂)_(n)COOR₅(n=0-1) or—(CH₂)_(n)COOR₆(n=0-1); R₅ represents C₁₋₅ alkyl group, C₁₋₅ substitutedalkyl group, alicyclic group, substituted alicyclic group, aromaticgroup or substituted aromatic group; and R₆ represents t-butyl group,t-amyl group, dimethylbenzyl group, tetrahydropyranyl group or3-oxocyclohexyl group).

In the above-described radiation sensitive material, it is preferredthat the copolymer is expressed by

(where l, m and n represent 1-95 mol %, 10-95 mol % and 5-50 mol %; Zrepresents benzene ring, substituted benzene ring, nitrile group, —OR₇,—COR₇ or —OCOR₇; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkylgroup, C₁₋₄ substituted alkyl group, nitrile group,—C(CH₂)_(n)COOR₅(n=0-1), or —(CH₂)_(n)COOR₆(n=0-1); R₆ representst-butyl group, t-amyl group, dimethylbenzyl group, tetrahydropyranylgroup or 3-oxocyclohexyl group; R₇ represents C₁₋₅ alkyl group, C₁₋₅substituted alkyl group, alicyclic group, substituted alicyclic group,aromatic group or substituted aromatic group).

In the above-described radiation sensitive material, it is preferredthat the copolymer is expressed by a general formula

(where l, m and n represent 0-95 mol %, 1-95 mol % and 5-50 mol %; R₁,R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkyl group, C₁₋₄ substitutedalkyl group, nitrile group, —(CH₂)_(n)COOR₅(n=0-1) or—(CH₂)_(n)COOR₆(n=0-1); R₅ represents C₁₋₅ alkyl group, C₁₋₅ substitutedalkyl group, alicyclic group, substituted alicyclic group, aromaticgroup or substituted aromatic group; and R₈ represents —OtBu, —OCOOtBuor —COOt-Amyl).

In the above-described radiation sensitive material, the copolymer isexpressed by a general formula

(where l, m and n represent 0-95 mol %, 1-95 mol % and 5-50 mol %; Zrepresents benzene ring, substituted benzene ring, nitrile group, OR₇,—COR₇ or —OCOR₇; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkylgroup, C₁₋₄ substituted alkyl group, nitrile group,—(CH₂)_(n)COOR₅(n=0-1) or —(CH₂)_(n)COOR₆(n=0-1); and R₈ represents—OtBu, —OCOOtBu, or —COOt-Amyl).

In the above-described radiation sensitive material, it is preferredthat the copolymer includes the unit structure including itaconicanhydride by 5-50 mol %.

The above-described object of the present invention is achieved by amethod for forming a pattern comprising the steps of: preparing a resistof the above-described radiation sensitive material; applying the resistto a substrate to be processed; prebaking the resist film and thenselectively exposing the resist on the substrate to radiation; and postexposure baking and then developing the resist on the substrate to formthe pattern.

The above-described object of the present invention is achieved by amethod for forming a pattern comprising the steps of: preparing a resistof a radiation sensitive material; applying the resist to a substrate tobe processed; prebaking the resist film and then selectively exposingthe resist on the substrate to radiation; and post exposure baking thesubstrate and then developing the resist on the substrate by a developerbeing a mixed liquid of an organic alkaline aqueous solution andisopropyl alcohol to form the pattern.

Here the radiation sensitive material preferably comprises: a copolymerincluding a unit structure including alicyclic groups, e.g., adamantylgroups, norbornyl group, and a unit structure generating an alkalisoluble group in the presence of an acid; and a substance generating anacid by application of radiation.

In the above-described radiation sensitive material, it is preferablethat the developer contains isopropyl alcohol by 5-95 vol %.

The above-described object is achieved by a method for forming a patterncomprising the steps of: preparing a resist of a polymer containing anacrylic or methacrylic ester unit, having an alicyclic group at saidacrylic or methacrylic ester unit; where said acrylic or methacrylicester unit have a polar structure at an ester unit; coating a substrateto be processed with the resist, and prebaking the substrate to beprocessed; applying onto the resist a protecting film of ahydrocarbon-based polymer, which is transparent to far ultraviolet rays,and heating the same; selectively exposing radiation to the resist onthe substrate to be processed; postbaking the substrate to be processed;stripping the protecting film; and developing the resist on thesubstrate to be processed to form a desired resist pattern, anapplication solvent for the hydrocarbon-based polymer of the protectingfilm being a non-aromatic hydrocarbon, or an aromatic hydrocarbonexpressed by a general formula

(where R represents an alkyl group with 3 or more carbon atoms).

The above-described object of the present invention is achieved by amethod for forming a pattern comprising the steps of forming a resist ofa radiation sensitive material according to any one of claims 26 to 31;coating a substrate-to-be-processed with the resist, and prebaking thesubstrate to be processed; applying a protecting film of a hydrocarbonpolymer, which is transparent to far ultraviolet rays, and heating thesame; selectively exposing radiation to the resist on the substrate tobe processed, and postbaking the substrate to be processed; andstripping the protecting film, and developing the resist on thesubstrate to be processed to form a desired resist pattern.

In the above-described method for forming a pattern, it is preferredthat an application solvent for the hydrocarbon polymer for theprotecting film is limonene, 1,5-cyclooctadiene, 1-decene,t-butylcyclohexane, p-cymene or dodecylbenzene.

In the method for forming a pattern, it is preferred that thehydrocarbon polymer is an olefine polymer or a diene polymer.

In the above-described method, the substance having a polar-structure isketone, alcohol, ether, ester, carbonic acid, an acid anhydride or anyone of these substances having a part of the atoms of a polar structure.

A substance generating an acid by application of radiation used in theabove-described radiation sensitive material, i.e., an acid generatingsubstance can be provided by:

an oxazole derivative expressed by the general formula

(where R₁ represents a substituted or an unsubstituted aryl group oralkenyl group; and X represents Cl or Br),

an s-triazine derivative expressed by the general formula

(where R₁ represents CH₃, a substituted or an unsubstituted alkyl group,or a substituted or an unsubstituted aryl or alkenyl group; and Xrepresents Cl or Br),

an iodonium salt expressed by the general formula

(where Ar₁ and Ar₂ represent a substituted or an unsubstituted aromaticring; and X represents BF₆ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻ or ClO₄ ⁻ or anorganic sulfonic acid anion),

a sulfonium salt expressed by the general formula

(where R₁, R₂ and R₃ represent a substituted or an unsubstituted alkylgroup, or an aromatic ring; X represents BF₆ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻ orClO₄ ⁻, or an organic sulfonic acid anion),

a disulfone derivative expressed by the general formulaR₁—SO₂—SO₂—R₂(where R₁ and R₂ represent a substituted aromatic ring or an alicyclicgroup),

an imidosulfonate derivative expressed by the general formula

(where R₁ represents a substituted or unsubstituted alkyl group or arylgroup; and Z represents a substituted or unsubstituted alkylene group,alkeneylene group or aryl group), or

a diazonium salt expressed by the general formulaAr₁—N₂ ⁺Y⁻(where Ar₁ represents a substituted or an unsubstituted aromatic ring; Yrepresents BF₆ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻ or ClO₄ ⁻, or an organicsulfonic acid anion). But the acid generating substance is not limitedto the above-described substances.

In the radiation sensitive material comprising a copolymer expressed bythe following general formula

(where Y represents alicyclic group; R₁ and R₂ represent CH₃ or H, andat least one of R₁ and R₂ is H; and R₃ represents alkyl group); and anacid generating material by application of radiation, either of R₁ andR₂ at the α positions is not a methyl group, which is bulky and veryhydrophobic, but a proton, which is small-sized and less hydrophobic.Accordingly the copolymer is less hydrophobic and less rigidity.Consequently the copolymer is more compatible with and permeable to adeveloper, while protonic acid as a catalyst can be more diffusible.Development is therefore easier, resulting in higher sensitivity andstable patterning characteristics.

Here it is preferable that this copolymer contains a unit structurecontaining alicyclic groups by 40-70 mol %. In the composition withbelow 40 mol % of the unit structure, sufficient dry etching resistancecannot be obtained. The composition with above 70 mol % of the unitstructure makes patterning difficult because of a small amount oft-butyl, a photosensitive group.

The radiation sensitive material comprising a copolymer expressed by thefollowing general formula

(where R₁ represents CH₃ or H); and an acid generating substance byapplication of radiation can have higher sensitivity and stablepatterning characteristics because of the carboxylic acid contained inthe copolymer, which is an effective hydrophilic group.

That is, because carboxylic acid is alkali soluble, the copolymeroriginally containing carboxylic acid becomes an alkaline aqueoussolution only by substitution of the sensitive groups by a small amountof carboxylic acid. Accordingly, high sensitivity and stable patterningcharacteristics can be obtained.

In the radiation sensitive material comprising a terpolymer expressed bythe following general formula

(where Y represents alicyclic group;

-   Z represents —C(CH₃)₂R₄,-   R₁, R₂, and R₃ represent CH₃ or H; and R₄ represents alkyl group);    and a substance generating acid by application of radiation, it is    very effective that the terpolymer contains carboxylic acid, which    is hydrophilic, because the terpolymer contains alicyclic groups,    which are very hydrophobic.

It is preferable that the terpolymer contains carboxylic acid by above 5mol % and below 35 mol %. This is because with a carboxylic acid contentof below 5 mol %, the effect is-not exhibited, and with a carboxylicacid content of above 35 mol %, even non-exposed portions are solved andthus patterning is impossible.

In the radiation sensitive material comprising a copolymer including aunit structure, which is expressed by the following general formula

and which generates alkali soluble groups in the presence ofhydroxyethyl methacrylate and an acid, and an acid generating substanceby application of radiation, the copolymer contains hydroxyethylmethacrylate as hydrophilic groups, whereby as in the case that thecopolymer contains carboxylic acid, the copolymer has higherhydrophilicity, and thus is more compatible with a developer and ispermeable, resulting in higher solubility.

In the radiation sensitive material comprising a terpolymer containing aunit structure which is expressed by the following general formula

(where Y represents alicyclic group;

-   Z represents —C(CH₃)₂R₄,-   R₁ and R₂ represent CH₃ or H; and R₃ represents alkyl group); and an    acid generating substance by application of radiation, because the    terpolymer contains alicyclic groups, which are very hydrophobic, it    is very effective that the terpolymer contains hydroxyethyl    methacrylate as a hydrophobic group.

It is preferable that the terpolymer contains hydroxyethyl methacrylateby above 5 mol % because the effect is not exhibited with a content ofhydroxyethyl methacrylate below 5 mol %.

The radiation sensitive material comprising a copolymer including a unitstructure expressed by the following general formula

(where X₁, and X₂ represent —C(CH₃)₂R₁,

and R₁ represents alkyl group); and a unit structure generating analkali soluble group in the presence of an acid, and an acid generatingsubstance by application of radiation; and

the radiation sensitive material comprising a copolymer expressed by thefollowing general formula

(where X₁ and X₂ represent —C(CH₃)₂R₂,

Y represents alicyclic group; R₁ represent CH₃ or H; and R₂ representsalkyl group); and an acid. generating substance by application ofradiation, both include a unit structure expressed by

(where X₁ an X₂ represent —C(CH₃)₂R₁,

and R₁ represents alkyl group); whereby a larger number of sensitivegroups are available per unit structure, with a result that highersensitivity can be obtained, resulting in stable patterningcharacteristics.

The radiation sensitive material comprising a copolymer including a unitstructure expressed by the following formula

(where X₁ an X₂ represent —C(CH₃)₂R₁,

and R₁ represents alkyl group); and a unit structure generating alkalisoluble groups in the presence of an acid, and an acid generatingsubstance by application of radiation; and

the radiation sensitive material comprising a copolymer expressed by thefollowing general formula

(where X₁ and X₂ represent —C(CH₃)₂R₂,

Y represents alicyclic group; R₁ represents CH₃ or H; and R₂ representsalkyl group); and an acid generating substance by application ofradiation, both include a unit structure expressed by

(where X₁ an X₂ represent —C(CH₃)₂R₁,

and R₁ represents alkyl group); whereby a larger number of sensitivegroups is available per unit structure, and thus higher sensitivity andstable pattering characteristics can be obtained.

For more stable patterning characteristics, it is effective to improveadhesiveness. The presence of especially adamantyl groups and t-butylgroups, which are hydrocarbon, degrades adhesiveness. This is becausehydrocarbon-based groups have such low polarity that there is nointeraction with a substrate.

Accordingly the radiation sensitive material comprising a copolymerincluding a unit structure expressed by the following general formula

(where at least one of X and Y is nitrile group), and a unit structuregenerating alkali soluble groups in the presence of an acid, and an acidgenerating substance by application of radiation can have improvedadhesiveness and stable patterning characteristics because of thenitrile groups, which have high polarity.

In the case that the unit structure including nitrile groups isacrylonitrile or methacrylonitrile, its content is preferably 10-70 mol%. When its content is below 10 mol %, sufficient adhesiveness cannot beobtained, and when its content is above 70 mol %, sufficient sensitivitycan not be obtained.

A radiation sensitive material comprising a polymer expressed by ageneral formula

(where X represents H or CH₃;

-   R represents    and-   R₁ and R₂ represent H, R₃ represents-   R₁ represents CH₃, R₂ represents H, R₃ represents-    or-   R₁ and R₂ represent CH₃, R₃ represents-    or-   R₁, R₂ and R₃ represents CH₃); containing hydrophilic groups and    highly hydrophobic groups (e.g., adamantyl, norbornyl, cyclohexyl);    and a substance generating an acid by application of radiation; and    a radiation sensitive material comprising a copolymer which is    expressed by a general formula-   (where X represents H or CH₃;-   R represents-    and-   R₁ and R₂ represent H, R₃ represents-   R₁ represents CH₃, R₂ represents H, R₃ represents-    or-   R₁ and R₂ represent CH₃, R₃ represents-    or-   R₁, R₂ and R₃ represents CH₃); or a copolymer containing hydrophilic    groups and expressed by a general formula-   (where R represents-    and-   a highly hydrophobic compound expressed by a general formula-   or by a general formula-   (where R₁ and R₂ represent-    or-   R₁ represents-    R₂ represents-   are inhibited by the highly hydrophobic groups from deactivation due    to contaminants (amine, etc.) in environments from the exposure to    the baking, and can have high sensitivity simply by changing    photosensitive groups to a small amount of alkali soluble    hydrophilic groups, so that resists especially those containing    highly hydrophobic groups can be stably patterned.

Here, when the hydrophilic group-content copolymer contains an excessiveratio of vinylphenol expressed by the structural formula

the copolymer is soluble in a developer, so that even unexposed partsare solved, and patterns cannot be formed. When the vinylphenol iscontained by a too small ratio, resists cannot be well stripped so thatstable patterning cannot be conducted. Thus it is preferred that thehydrophilic group-content copolymer expressed by a structural formula

-   (where X represents H or CH₃;-   R represents-    and-   R₁ and R₂ represent H, R₃ represents-   R₁ represents CH₃, R₂ represents H, R₃ represents-   R₁ and R₂ represent CH₃, R₃ represents-    or-   R₁, R₂ and R₃ represent CH₃); contains vinylphenol by 50-70 mol %.    It is preferred that the hydrophilic group-content copolymer    expressed by the structural formula-   (where R represents    contains vinylphenol by 60-80 mol %.

By use of the radiation sensitive material comprising a copolymerincluding itaconic anhydride which is expressed by

and a polymer as a unit structure which generates an alkali solublegroup in the presence of an acid, and by use of a substance generatingan acid by application of radiation, resists which have good adhesioncan be formed. That is, because of the strong polarity of itaconicanhydride, adhesion of resists to substrates can be greatly improved.

Itaconic anhydride itself exhibits solubility to alkali, and has to befed to use itaconic anhydride without impairing patterningcharacteristics. A feed amount of itaconic anhydride is preferably 5-50mol % although this depends on compositions and structures of thepolymer. With a feed amount of 5 mol % exclusive of 5 mol %, theadhesion cannot be improved. With a feed amount exceeding 50 mol %, theresist itself becomes alkali soluble, the unexposed part of the resistis also resolved, and patterning is impossible.

Feed of such alkali soluble groups is very effective to improveresolubility of the pattern, and good patterning characteristics can beobtained.

The copolymer containing itaconic anhydride has specific structuresexpressed by the general formula

(where l, m and n represent 0-60 mol %, 10-95 mol %, 5-50 mol %respectively; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkyl group,C₁₋₄ substituted alkyl group, nitrile group, —(CH₂)_(n)COOR₅(n=0-1) or—(CH₂)_(n)COOR₆(n=0-1); R₅ represents C₁₋₅ alkyl group, C₁₋₅ substitutedalkyl group, alicyclic group, substituted alicyclic group, aromaticgroup or substituted aromatic group; and R₆ represents t-butyl group,t-amyl group, dimethylbenzyl group, tetrahydropyranyl group or3-oxocyclohexyl group),

(where l, m and n represent 1-95 mol %, 10-95 mol % and 5-50 mol %; Zrepresents benzene ring, substituted benzene ring, nitrile group, —OR₇,—COR₇ or —OCOR₇; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkylgroup, C₁₋₄ substituted alkyl group, nitrile group,—C(CH₂)_(n)COOR₅(n=0-1), or —(CH₂)_(n)COOR₆(n=0-1); R₆ representst-butyl group, t-amyl group, dimethylbenzyl group, tetrahydropyranylgroup or 3-oxocyclohexyl group; R₇ represents a C₁₋₅ alkyl group, C₁₋₅substituted alkyl group, alicyclic group, substituted alicyclic group,aromatic group or substituted aromatic group),

(where l, m and n represent 0-95 mol %, 1-95 mol % and 5-50 mol %; Zrepresents benzene ring, substituted benzene ring, nitrile group, OR₇,—COR₇ or —OCOR₇; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkylgroup, C₁₋₄ substituted alkyl group, nitrile group,—(CH₂)_(n)COOR₅(n=0-1) or —(CH₂)_(n)COOR₆(n=0-1); and R₈ represents—OtBu, —OCOOtBu, or —COOt-Amyl),

(where l, m and n represent 0-95 mol %, 1-95 mol % and 5-50 mol %; Zrepresents benzene ring, substituted benzene ring, nitrile group, OR₇,—COR₇ or —OCOR₇; R₁, R₂, R₃ and R₄ represent H, halogen, C₁₋₄ alkylgroup, C₁₋₄ substituted alkyl group, nitrile group,—(CH₂)_(n)COOR₅(n=0-1) or —(CH₂)_(n)COOR₆(n=0-1); and R₈ represents—OtBu, —OCOOtBu, or —COOt-Amyl), or other structures.

Here the so-called alicyclic group is adamantyl, norbornyl, cyclohexyl,a substance partially having tricyclo[5.2.1.0]decane skeleton or others,but is not limited to them.

Groups generating alkali soluble groups in the presence of an acid aret-butyl ester, t-amyl ester, t-butyl ether, t-BOC, tetrahydropyranyl,tetrahydropyranyl ether, 3-oxocyclohexyl ester or dimethylbenzyl ester,but is not limited to them.

That is, a resist is formed of the above-described radiation sensitivematerial, and the resist is applied onto a substrate to be processed,prebaked, exposed, postbaked and developed, and is subjected to othertreatments, whereby a submicron dimension patterns can be formed stably.

To obtain more stable patterning characteristics, it is necessary toimprove developers. Chemical amplifying resists have the intrinsicproblem that protonic acid becomes inactive on the surface layers due tocontamination by environmental amine, etc. Consequently solubilitydifferences take place between the surface and inner layers, which is aserious factor that hinders stable patterning. Especially adamantylgroups, t-butyl groups, etc., Hydrocarbons, which are very hydrophobic,especially adamantyl groups, t-butyl groups, etc., are effective tohinder dissolution in developers, and are very effective at making thesurface insoluble.

Accordingly, a mixed liquid of an organic alkaline aqueous solution andisopropyl alcohol is used as a developer, whereby solubility is muchimproved and smaller solubility differences between the surface andinner layers can be obtained, so allowing stable patterning. Isopropylalcohol is the most effective alcohol to be added as methanol andethanol cause cracks, and peelings are found. The use of this liquidmixture developer raised the sensitivity by one or more places andreduced strain caused upon development, so that the adhesiveness wasmuch improved.

It is preferable that the developer contains isopropyl alcohol by 5-95vol %. This is because content of isopropyl alcohol by below 5 mol %does not improve the sensitivity, and content above 95 mol % easilycauses cracks and crazes.

A polymer containing an acrylic or methacrylic ester unit, each havingan alicyclic group and a polar structure at an ester unit, has such ahigh base polymer polarity that the very high hydrophobicity due to thealicyclic group can be lowered. As a result, polarity differences occurbetween the polymer and the hydrocarbon-based protecting film, and theprotecting film can be applied without resolving the resist film,whereby a pattern of a desired size can be formed.

Examples of substances having high polarity structures are ketone,alcohol, ether, ester, carbonic acid, an acid anhydride, or any one ofthese substances having some of the atoms of their polar structurereplaced by sulfur, nitrogen or halogen atoms, but is not limited tothem.

The ratio of feed of the materials having polar structures must be atleast 1-50 mol %, preferably 20% or greater.

Although the resist containing itaconic anhydride contains highlyhydrophobic hydrocarbon groups, the resist permits hydrocarbon-basedpolymers, which have not been conventionally applied to the resist as aprotecting film because of the high polarity of itaconic anhydride.

Formation of such protecting films on the resist can avoid the problemof PED (Post Exposure Delay), which is characteristic of chemical widthincrement resists.

A high molecular weight hydrocarbon-based solvent is used as the solventfor application of the protecting film, so that the protecting film canbe applied with higher accuracy. Application solvents with too low aboiling point make it difficult to uniformly apply the protecting filmon wafers. Preferably solvents have boiling points above 100° C. areused. Examples of preferable solvents are limonene, 1,5-cyclooctadiene,1-decene, t-butylcyclohexane, p-cymene, dodecylbenzene, etc.

The hydrocarbon polymer is, for example, olefine, diene, etc. but is notlimited to them as long as the hydrocarbon polymers are transparent toexposure wavelengths and are soluble in the above-mentioned solvent.

The alicyclic group is, for example, cyclohexane, norbornane, adamantyl,and substances having a tricyclo[5.2.1.0]decane skeleton, but is notlimited to them.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the flow chart of one example of the semiconductor fabricationmethod according to the present invention;

FIGS. 2A to 2G are sectional views of a semiconductor device in thesteps of one example of the semiconductor fabrication method accordingto the present invention;

FIG. 3 is the flow chart of another example of the semiconductorfabrication method according to the present invention;

FIGS. 4A to 4H are sectional views of a semiconductor device in thesteps of another example of the semiconductor fabrication methodaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of the semiconductor fabrication method according to thepresent invention will be explained with reference to FIGS. 1, and 2A to2G.

In patterning a polycrystalline silicon film 14 deposited through anoxide film 13 on a semiconductor substrate 10 with a field isolation 12formed on as shown in FIG. 2A, a resist film 16 is applied to thesemiconductor substrate 10 with a polycrystalline silicon film 14 formedon (Step S11), and prebaked (Step S12) (FIG. 2B).

Then, the semiconductor substrate 10 with the resist film 16 depositedon is exposed through a mask 18 for selective exposure (Step S13, FIG.2C).

Following postbake (Step S14), the resist film 16 is developed with adeveloper (Step S15) and patterned. Subsequently the semiconductorsubstrate 10 is rinsed with deionized water (Step S16). Thus thepatterned resist film 16 is formed on the semiconductor substrate 10(FIG. 2D).

Then, with the patterned resist film 16 as a mask, the polycrystallinesilicon film 14 is etched by reactive ion etching (FIG. 2E).

Next, the resist film 16 is removed, and the patterning of thepolycrystalline silicon film 14 is completed (FIG. 2F).

Subsequently ion implantation is conducted with the polycrystallinesilicon film 14 as a mask to form a source/drain diffusion 20, and a MOStransistor including the polycrystalline silicon film 14 as a gateelectrode is fabricated (FIG. 2G).

Another example of the semiconductor fabrication method according to thepresent invention will be explained with reference to FIGS. 3, and 4A to4H.

In patterning a polycrystalline silicon film 14 deposited through anoxide film 13 on a semiconductor substrate 10 with a field isolation 12formed on as shown in FIG. 4A, a resist film 16 is applied to thesemiconductor substrate 10 with a polycrystalline silicon film 14 formedon (Step S21), and prebaked (Step S22, FIG. 4B).

Next, a protecting film 20 (top coat) is applied onto the semiconductorsubstrate 10 by spin coating (step S23), and prebaked (Step S24, FIG.4C)

Then, the semiconductor substrate 10 with the resist film 16 and theprotecting film 20 deposited on is exposed through a mask 18 forselective exposure (Step S25, FIG. 4D).

Following postbake (Step S26), chemical solution which can dissolve theprotecting film 20 is applied onto the semiconductor substrate 10 byspin coating, and the protecting film 20 is stripped (Step S27, FIG.4E).

Next, the resist film 16 is developed with a developer (Step S28) andpatterned. Subsequently the semiconductor substrate 10 is rinsed withdeionized water (Step S29). Thus the patterned resist film 16 is formedon the semiconductor substrate 10 (FIG. 4F).

Then, with the patterned resist film 16 as a mask, the polycrystallinesilicon film 14 is etched by reactive ion etching (FIG. 4G).

Next, the resist film 16 is removed, and the patterning of thepolycrystalline silicon film 14 is completed (FIG. 4H).

As described above, subsequently ion implantation is conducted with thepolycrystalline silicon film 14 as a mask to form a source/draindiffusion 20, and a MOS transistor including the polycrystalline siliconfilm 14 as a gate electrode is fabricated.

Accordingly micronized semiconductor device can be fabricated by excimerlaser lithography, which can provide highly sensitive, stable patterningcharacteristics.

EXAMPLE 1

Adamantyl methacrylate monomer, and t-butyl acrylate monomer were loadedby 1:1, and a 5 mol/l toluene solution was prepared. 20 mol % of AIBN(azoisobutylo nitrile) expressed by the following structural formula

was added as a polymerization initiator. Then polymerization was reactedat 80° C. for 8 hours, and precipitation purification followed. And acopolymer expressed by the following structural formula

and having a 58:42 composition ratio, a 5100 weight-averaged molecularweight (Mw) and a 1.43 (Mw/Mn) was prepared. A thermal analysis showedthat the glass transition temperature of this polymer was 126° C.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper (by Nikon, NA=0.45) and then was subjected to PEB (Post ExposureBake) at 100° C. for 60 seconds. Subsequently the resist was developedfor 60 seconds by NMD-3 (by Tokyo Ohka), which is an alkaline aqueoussolution and rinses by deionized water for 30 seconds. A thresholdenergy Eth of the radiation dose for this exposure was 50 mJ/cm². A 0.45μm-wide L & S (line and space) pattern was formed at a 130 mJ/cm²radiation dose.

EXAMPLE 2

Adamantyl acrylate monomer and t-butyl methacrylate monomer were loadedby 1:1, and a 5 mol/l toluene solution was prepared. 20 mol % of AIBN(azoisobutylo nitrile) was added as a polymerization initiator. Thenpolymerization was reacted at 80° C. for 8 hours, and precipitationpurification followed. And a copolymer expressed by the followingstructural formula

and having a 50:50 composition ratio, a 4180 weight-averaged molecularweight and a 1.59 degree of dispersion was prepared. A thermal analysisshowed that the glass transition temperature of this polymer was 94° C.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 81 mJ/cm². A 0.50 μm-wide L & S pattern was formed.

EXAMPLE 3

Adamantyl acrylate monomer, and t-butyl acrylate monomer were loaded by1:1, and a 5 mol/l toluene solution was prepared. 20 mol % of AIBN wasadded as a polymerization initiator. Then polymerization was reacted at80° C. for 8 hours, and precipitation purification with methanolfollowed. And a copolymer expressed by the following structural formula

and having a 47:53 composition ratio, a 4610 weight-average molecularweight and a 1.83 degree of dispersion was prepared. A thermal analysisshowed that the glass transition temperature of this polymer was 72° C.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 37 mJ/cm². A 0.50 μm-wide L & S pattern was formed.

[Control 1]

Adamantyl methacrylate monomer, and t-butyl methacrylate monomer wereloaded by 1:1, and a 5 mol/l toluene solution was prepared. 20 mol % ofAIBN was added as a polymerization initiator. Then polymerization wasreacted at 80° C. for 8 hours, and precipitation purification followed.And a copolymer expressed by the following structural formula

and having a 59:41 composition ratio, a 3351 weight-average molecularweight and a 1.31 degree of dispersion was prepared. No glass transitiontemperature of this polymer was found by a thermal analysis.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. The development did not advance, and no pattern was formed.

[Control 2]

Adamantyl methacrylate monomer, and t-butyl methacrylate monomer wereloaded by 1:1, and a 5 mol/l toluene solution was prepared. 20 mol % ofAIBN was added as a polymerization initiator. Then polymerization wasreacted at 80° C. for 8 hours, and precipitation purification followed.And a copolymer expressed by the following structural formula

and having a 47:53 composition ratio, a 19000 weight-averaged molecularweight and a 1.51 degree of dispersion was prepared. No glass transitiontemperature of this polymer was found by a thermal analysis.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. An exposed region was reduced to about 10% at a radiation doseof 102 mJ/cm², but the residual film did not disappear even at higherexposures.

EXAMPLE 4

Dimethyladamantyl acrylate monomer, and t-butyl methacrylate monomerwere loaded by 1:1, and a 5 mol/l toluene solution was prepared. 20 mol% of AIBN (azoisobutylo nitrile) was added as a polymerizationinitiator. Then polymerization was reacted at 80° C. for 8 hours, andprecipitation purification followed. And a copolymer expressed by thefollowing structural formula

and having a 47:53 composition ratio, a 3650 weight-averaged molecularweight and a 1.64 degree of dispersion was prepared. A thermal analysisshowed that the glass transition temperature of this polymer was 66° C.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 81 mJ/cm². A minimum resolution was a 0.35 μm-wide L & S.

EXAMPLE 5

Dimethyladamantyl acrylate monomer, and t-butyl acrylate monomer wereloaded by 1:1, and a 5 mol/l toluene solution was prepared. 20 mol % ofAIBN (azoisobutylo nitrile) was added as a polymerization initiator.Then polymerization was reacted at 80° C. for 8 hours, and precipitationpurification followed. And a copolymer expressed by the followingstructural formula

and having a 50:50 composition ratio, a 4050 weight-averaged molecularweight and a 1.71 degree of dispersion was prepared. A thermal analysisshowed that the glass. transition temperature of this polymer was 47° C.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 81 mJ/cm². A minimum resolution was a 0.30 μm-wide L & S.

[Control 3]

Adamantyl methacrylate monomer, and t-butyl methacrylate monomer wereloaded by 3:7, and a 5 mol/l toluene solution was prepared. 20 mol % ofAIBN (azoisobutylo nitrile) was added as a polymerization initiator.Then polymerization was reacted at 80° C. for 8 hours, and precipitationpurification followed. And a copolymer expressed by the followingstructural formula

and having a 30:70 composition ratio, a 8400 weight-averaged molecularweight and a 1.61 degree of dispersion was prepared. No glass transitiontemperature of this polymer was not found by a thermal analysis.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 81 mJ/cm². A minimum resolution was a 0.50 μm-wide L & S, andsmaller patterns peeled off and could not be found.

EXAMPLE 6

Adamantyl methacrylate monomer, t-butyl methacrylate monomer andmethacrylic acid were loaded by 2:1:1. 0.5 mol/l 1,4-dioxane solutionwas used, and 20 mol % of AIBN was added as a polymerization initiator.Then polymerization was reacted at 80° C. for 8 hours, and precipitationpurification with n-hexane followed. And a terpolymer expressed by thefollowing structural formula

and having a 59:27:14 composition ratio, a 6242 weight-averagedmolecular weight and a 2.14 degree of dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 100 mJ/cm². A 0.45 μm-wide L & S pattern was formed.

EXAMPLE 7

A profile of the 1 μm hole pattern prepared according to Example 6 wasobserved. The result of the observation was no unsolved superficiallayer was found. Even when the resist film was exposed and then left for45 minutes, and was subjected to PEB, the pattern was not formed.

[Control 4]

Adamantyl methacrylate monomer, and t-butyl acrylate monomer were loadedby 1:1, and 5 mol/l toluene solution was prepared. 20 mol % of AIBN wasadded as a polymerization initiator. The polymerization was reacted forabout 8 hours at 80° C. The polymerization was followed by precipitationpurification with methanol. Resultantly a copolymer expressed by

and having a composition ratio of 59:42, a 5100 weight-average molecularweight, and a 1.43 degree of dispersion was prepared. The glasstransition temperature of this copolymer given by thermal analysis was126° C.

Then triphenylsulfonium hexaf luoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds by NMD-3, which isan alkaline aqueous solution and rinsed by deionized water for 30seconds. A threshold energy Eth of the radiation dose for this exposurewas 50 J/cm². A 0.45 μm wide L & S pattern was formed at 130 mJ/cm². Theprofile of a 1 μm hole pattern had “eaves” of an unsolved superficiallayer.

[Control 5]

In Control 4, after the exposure, the resist film was left for 45minutes and was subjected to PEB. A substantially upper half of thepattern was covered with the superficial unsolved layer. Accordingly thepattern could not be formed.

EXAMPLE 8

Adamantyl methacrylate monomer, t-butyl methacrylate monomer andmethacrylic acid were loaded by 2:1:1, and 0.5 mol/l 1,4-dioxanesolution was prepared. 20 mol % of AIBN was added as a polymerizationinitiator. Then polymerization was reacted at 80° C. for about 8 hours,and precipitation purification with n-hexane followed. And a terpolymerexpressed by the following structural formula

and having a 53:27:20 composition ratio, a 4523 weight-averagedmolecular weight and a 1.92 degree of dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula.

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 130° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was immersed for 90 seconds in an NMD-3solution, an alkaline aqueous solution, diluted by a 20-time amount ofdeionized water and developed, and then rinsed with deionized water for30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 57 mJ/cm². A 0.30 μm-wide L & S pattern was formed.

[Control 6]

Adamantyl methacrylate monomer, t-butyl methacrylate monomer andmethacrylic acid were loaded by 2:1:4, and 0.5 mol/l 1,4-dioxanesolution was prepared. 20 mol % of AIBN was added as a polymerizationinitiator. Then polymerization was reacted at 80° C. for about 8 hours,and precipitation purification with n-hexane followed. And a terpolymerexpressed by the following structural formula

and having a 43:31:36 composition ratio, a 4115 weight-averagedmolecular weight and a 1.95 degree of dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 130° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was immersed for 90 seconds in an NMD-3solution, an alkaline solution, diluted by a 20-time amount of deionizedwater, and the resist film disappeared.

EXAMPLE 9

To adamantyl methacrylate-t-butyl methacrylate-hydroxyethyl methacrylateterpolymer expressed by the following structural formula

and having a composition ratio of 53:44:4, a 8800 weight-averagemolecular weight and a 1.84 degree of dispersion, 15 wt % oftriphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance to prepare a cyclohexanonesolution. This solution was applied to an Si wafer treated with HMDS(hexamethyldisilazane) and then baked on a hot plate of 60° C. for 100seconds. And a 0.65 μm-thickness resist film was prepared.

The thus-prepared resist film was exposed by a KrF excimer stepper andwas subjected to PEB at 130° C. for 60 seconds. Subsequently the resistfilm was developed with an aqueous solution of 2.38% of TMAH(tetramethyl ammonium hydroxide). The radiation dose for this exposurewas 110 mJ/cm². A 0.4 μm-wide L & S pattern was resolved.

EXAMPLE 10

To adamantyl methacrylate-t-butyl methacrylate-hydroxyethyl methacrylateterpolymer expressed by the following structural formula

and having a composition ratio of 48:40:12, a 8400 weight-averagemolecular weight and a 1.94 degree of dispersion, 15 wt % oftriphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance to prepare a cyclohexanonesolution. This solution was applied to an Si wafer treated with HMDS(hexamethyldisilazane) and then baked on a hot plate of 60° C. for 100seconds. And a 0.65 μm-thickness resist film was prepared.

The thus-prepared resist film was exposed by a KrF excimer stepper andwas subjected to PEB at 130° C. for 60 seconds. Subsequently the resistfilm was developed with an aqueous solution of 2.38% of TMAH(tetramethylammonium hydroxide). The radiation dose for this exposurewas 40 mJ/cm². A 0.4 μm-wide L & S pattern was resolved.

[Control 7]

To adamantyl methacrylate-t-butyl methacrylate copolymer expressed bythe following structural formula

and having a composition ratio of 61:39, a 7900 weight-average molecularweight and a 1.82 degree of dispersion, 15 wt % of triphenylsulfoniumhexafluoroantimonate expressed by the following structural formula

was added as an acid generating substance to prepare a cyclohexanonesolution. This solution was applied, by spin coating, to a wafer coatedwith hard-baked novolak and baked on a hot plate of 60° C. for 100seconds. And a 0.65 μm-thickness resist film was formed.

The thus-prepared resist film was exposed by a KrF excimer stepper andwas subjected to PEB at 100° C. for 60 seconds. Subsequently the resistfilm was developed with an aqueous solution of 2.38% of TMAH(tetramethylammonium hydroxide). The radiation dose for this exposurewas 40 mJ/cm². A 0.4 μm-wide L & S pattern was resolved, but the patterncould not be reproduced.

EXAMPLE 11

Adamantyl methacrylate monomer, and di-t-butyl itaconate monomer wereloaded by 1:3. 20 mol % of MAIB (dimethyl 2,2-azoisobisbutylate)expressed by the following structural formula

was added as a polymerization initiator. Then, bulk polymerizationfollowed at 80° C. for about 3 hours. The polymerization was followed byprecipitation purification with methanol.

Resultantly the copolymer expressed by the following structural formula

and having a composition ratio of 59:41, a weight-average molecularweight of 9357 and a 2.44 degree of dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied, in a 0.7 μm-thickness by spin coating, to anHMDS treated Si wafer, and prebaked for 100 seconds on a hot plate of60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, whichis a alkaline aqueous solution, and then rinsed with deionized water for30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 5.6 mJ/cm². A resolution was a 0.7 μm-wide L & S pattern.

[Control 8]

Adamantyl methacrylate monomer, and t-butyl acrylate monomer were loadedby 1:1. 20 mol % of MAIB expressed by the following structural formula

was added as a polymerization initiator. Then, bulk polymerizationfollowed at 80° C. for about 3 hours with toluene as a reaction solvent.The polymerization was followed by precipitation purification withmethanol.

Resultantly the copolymer expressed by the following structural formula

and having a composition ratio of 59:41, a weight-average molecularweight of 6061 and a 1.24 degree of dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied, in a 7 μm-thickness by spin coating, to anHMDS treated Si wafer, and prebaked for 100 seconds on a hot plate of60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, whichis a alkaline aqueous solution, and then rinsed with deionized water for30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 25.1 mJ/cm². A minimum resolution was a 0.5 μm-wide L & Spattern.

EXAMPLE 12

To di-t-butyl itaconate monomer, 20 mol % of MAIB expressed by thefollowing structural formula

was added. Then bulk polymerization followed at 80° C. for about 9.5hours. The polymerization was followed by precipitation purificationwith methanol. Resultantly the copolymer expressed by the followingstructure formula

and having a weight-averaged molecular weight of 6061 and a 1.24 degreeof dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied, in a 0.7 μm-thickness by spin coating, to anHMDS treated Si wafer, and prebaked for 100 seconds on a hot plate of60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, whichis a alkaline aqueous solution, and then rinsed with deionized water for30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 7 mJ/cm². A resolution was a 0.5 μm-wide L & S pattern at a11 mJ/cm₂ radiation dose.

EXAMPLE 13

Adamantyl methacrylate monomer, and di-t-butyl fumarate monomer wereloaded by 1:3, and 20 mol % of MAIB expressed by the followingstructural formula

was added. Then bulk polymerization followed at 80° C. for about 25hours. The polymerization was followed by precipitation purificationwith methanol. Resultantly the copolymer expressed by the followingstructure formula

and having a composition ratio of 36:64 and a weight-average of 22645and a 2.44 degree of dispersion was prepared.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied, in a 0.7 μm-thickness by spin coating, to anHMDS treated wafer, and prebaked for 100 seconds on a hot plate of 60°C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, whichis a alkaline aqueous solution, and then rinsed with deionized water for30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 5 mJ/cm². A resolution was a 0.5 μm-wide L & S pattern.

[Control 9]

To the adamnatylacrylate-t-butyl methacrylate copolymer expressed by thefollowing structural formula

and having a composition ratio of 30:70, a weight-averaged molecularweight of 844 and a 1.61 degree of dispersion, 15 wt % oftriphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

as a polymerization initiator was added, and a cyclohexanone solutionwas prepared. This solution was applied, by spin coating, to a wafercoated with hard-baked novolak and baked on a hot plate of 60° C. for100 seconds. And a 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper, then subjected to PEB at 100° C. for 60 seconds, and developedwith a 2.38% TMAH aqueous solution, The threshold energy Eth of theradiation dose for this exposure was 15 mJ/cm². A 0.4 μm-wide L & Spattern was resolved, and the pattern could not be reproduced.

EXAMPLE 14

Methacrylonitrile monomer and t-butyl methacrylate were loaded by 1:1,and 5 mol/l of 1,4-dioxane solvent and 1 mol % of AIBN as apolymerization initiator were added. Polymerization was reacted at 80°C. for about 8 hours. The polymerization was followed by precipitationpurification with an aqueous methanol solution (methanol:water=2:1).Resultantly the polymerization expressed by the following structuralformula

and having a composition ratio of 41:59, a weight-average molecularweight of 16400 and a 1.77 degree of dispersion was prepared. Thecopolymer had a 98% transmittance for a 1 μm film thickness at the KrFlaser wavelength.

Then, 13 wt % cyclohexanone solution of this copolymer was prepared, andto this solution, 15 wt % of triphenylsulfonium hexafluoroantimonateexpressed by the following structural formula

was added as an acid generating substance to prepare a resist solution.This solution was applied, by spin coating, to an HMDS treated Si wafer,and prebaked for 100 seconds on a hot plate of 100° C. And a 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper, and then immersed in 2.38% TMAH aqueous solution for 60 secondsfor development. At a 70 mJ/cm² radiation dose, a 0.3 μm-wide L & Spattern was resolved.

EXAMPLE 15

Acrylonitrile monomer and t-butyl methacrylate were loaded by 3:7, and 5mol/l of 1,4-dioxane solvent and 1 mol % of AIBN as a polymerizationinitiator were added. Polymerization was reacted at 80° C. for about 8hours. The polymerization was followed by precipitation purificationwith an aqueous methanol solution (methanol:water=2:1). Resultantly thepolymerization expressed by the following structural formula

and having a composition ratio of 25:75, a weight-average molecularweight of 18800 and a 1.73 degree of dispersion was prepared. Thecopolymer had a 98% transmittance for a 1 μm film thickness at the KrFlaser wavelength.

Then, using this copolymer, a pattern was formed in the same process asin Example 14. A 0.35 μm-wide L & S pattern was resolved.

EXAMPLE 16

Methacrylonitrile monomer and t-butyl methacrylate were loaded by 1:1,and 5 mol/l of 1,4-dioxane solvent and 1 mol % of AIBN as apolymerization initiator were added. Polymerization was reacted at 80°C. for about 8 hours. The polymerization was followed by precipitationpurification with an aqueous methanol solution (methanol:water=2:1).Resultantly the polymerization expressed by the following structuralformula

and having a composition ratio of 43:57, a weight-average molecularweight of 31800 and a 1.53 degree of dispersion was prepared.

Then, using this copolymer, a pattern was formed in the same process asin Example 14. A 0.35 μm-wide L & S pattern was resolved.

[Control 10]

5 mol/l of a solvent, 1,4-dioxane, and 1 mol % of AIBN, a polymerizationinitiator, were added to t-butyl methacrylate monomer, andpolymerization was reacted at 80° C. for about 8 hours. Thepolymerization was followed by precipitation purification with anaqueous solution of methanol (methanol:water=2:1). Resultantly thehomopolymer expressed by the following structural formula

and having a weight-averaged molecular weight of 36000, and a 1.82degree of dispersion was prepared.

Then, using this copolymer, a pattern was formed in the same process asin Example 14. L & S patterns of below 1 μm-wide peeled off.

EXAMPLE 17

Three kinds of monomers of methacrylonitrile, t-butyl methacrylate, andadamantyl methacrylate were loaded by 1:2:1, and 1 mol/l of a solvent,1,4-dioxane, and 1 mol % of AIBN, a polymerization initiator were added.Polymerization was reacted at 80° C. for about 8 hours. Thepolymerization was followed by precipitation purification with anaqueous solution of methanol (methanol:water=2:1). Resultantly theterpolymer expressed by the following structural formula

and having a composition ratio of 10:54:36, a weight-averaged molecularweight 5750 and a 1.21 degree of dispersion was prepared.

Then, using this copolymer, a pattern was formed in the same process asin Example 14. A 0.7 μm-wide L & S pattern was resolved at a 250 mJ/cm²radiation dose.

[Control 11]

Using t-butyl methacrylate-adamantyl methacrylate copolymer of acomposition ratio of 70:30, patterns were formed in the same process asin Example 14. The patterns were completely peeled off.

EXAMPLE 18

15 wt % cyclohexanone solution of adamantyl methacrylate-3-oxocyclohexylmethacrylate copolymer expressed by the following structural formula

and having a composition ratio of 41:59, a 13900 weight-averagedmolecular weight and a 1.51 degree of dispersion was prepared. To thissolution, 15 wt % of triphenylsulfonium hexafluoroantimonate expressedby the following structural formula

was added as an acid generating substance to prepare a resist solution.This solution was applied by spin coating to a wafer coated withhard-baked novolak resin and baked for 100 seconds on a hot plate of100° C. A 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper, and then subjected to PEB for 60 seconds. Subsequently theresist film was immersed in mixed liquid of 2.38% TMAH aqueous solutionand isopropyl alcohol mixed by a volume ratio of 1:1 for 60 seconds fordevelopment. At a 26 mJ/cm² radiation dose, a 0.25 μm-wide L & S patternwas resolved.

[Control 12]

The same process as in Example 18 was conducted, and a PEB treated waferwas immersed in 2.38% TMAH aqueous solution for 60 seconds fordevelopment. The minimum resolved pattern was 0.45 μm-wide L & S.

EXAMPLE 19

15 wt % cyclohexanone solution of adamantyl methacrylate-3-oxocyclohexylmethacrylate copolymer expressed by the following structural formula

and having a composition ratio of 41:59, a 13900 weight-averagedmolecular weight and a 1.51 degree of dispersion was prepared. To thissolution, 15 wt % of triphenylsulfonium hexafluoroantimonate expressedby the following structural formula

was added as an acid generating substance to prepare a resist solution.This solution was applied by spin coating to a wafer treated with HMDS(hexamethyl disilazane), and baked for 100 seconds on a hot plate of100° C. A 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper, and then subjected to PEB for 60 seconds. Subsequently theresist film was immersed in mixed liquid of 2.38% TMAH aqueous solutionand isopropyl alcohol mixed by a volume ratio of 1:1 for 60 seconds fordevelopment. At a 32 mJ/cm² radiation dose, a 0.30 μm-wide L & S patternwas resolved.

[Control 13]

The same process as in Example 19 was conducted, and a PEB treated waferwas immersed in 2.38% TMAH aqueous solution for 60 seconds fordevelopment. Patterns of below 1 μm were completely peeled off.

EXAMPLE 20

Adamantyl methacrylate monomer and t-butyl methacrylate monomer wereloaded by 1:1, and 5 mol/l toluene solution was prepared. 20 mol % ofAIBN was added as a polymerization initiator. Then polymerization wasreacted at 80° C. for about 8 hours, and precipitation purification withmethanol followed. And a copolymer expressed by the following structuralformula

and having a 59:41 composition ratio, a 3351 weight-average molecularweight and a 1.31 degree of dispersion was prepared. No glass transitiontemperature of this polymer was found by a thermal analysis.

Then triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added as an acid generating substance by 15 wt % to thethus-synthesized copolymer, and a cyclohexanone solution was prepared.This solution was applied by spin coating in a 0.7 μm-thickness onto awafer coated with hard-baked novolak resin, and prebaked for 100 secondson a hot plate of 60° C.

The thus-prepared resist film on the wafer was exposed by KrF excimerstepper and then was subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with mixed liquidof an alkaline aqueous solution, NMD-3 and isopropyl alcohol mixed by avolume ratio of 1:1, and rinsed with deionized water for 30 seconds. Thethreshold energy Eth of the radiation dose for this exposure was 8mJ/cm². The minimum resolved pattern was a 0.30 μm-wide L & S.

EXAMPLE 21

The same process as in Example 20 was conducted. As a developmentliquid, the mixed liquid in Example 20 was replaced by mixed liquid ofNMD-3 and isopropyl alcohol mixed by a volume ratio of 3:3 was used. A0.40 μm-wide L & S pattern was resolved at a 42 mJ/cm² radiation dose.

EXAMPLE 22

The same process as in Example 20 was conducted. As a developmentliquid, the mixed liquid in Example 20 was replaced by mixed liquid ofNMD-3 and isopropyl alcohol mixed by a volume ratio of 9:1 was used. A0.40 μm-wide L & S pattern was resolved at a 98 mJ/cm² radiation dose.

[Control 14]

The same process as in Example 20 was conducted. As a developer, themixed liquid in Example 20 was replaced by isopropyl alcohol. A patterncompletely peeled off.

EXAMPLE 23

15 wt % cyclohexanone solution of adamantyl methacrylate-3-oxocyclohexylmethacrylate copolymer expressed by the following structural formula

and having a composition ratio of 41:59, a 13900 weight-averagedmolecular weight and a 1.51 degree of dispersion was prepared. To thissolution, 1 wt % of triphenylsulfonium hexafluoroantimonate expressed bythe following structural formula

was added to the polymer to prepare a resist solution. This solution wasapplied by spin coating to a wafer coated with hard-baked novolak resin,and baked for 100 seconds on a hot plate of 100° C. And a 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by an KrF excimerstepper, and then subjected to PEB at 150° C. for 60 seconds.Subsequently the resist film was immersed in mixed liquid of 2.38% ofTMAH aqueous solution and isopropyl alcohol by a 1:1 volume ratio fordevelopment. A 0.35 μm-wide L & S pattern was resolved at a 88 mJ/cm²radiation dose.

[Control 15]

Using adamantyl methacrylate-t-butyl methacrylate copolymer expressed bythe following structural formula

the same process as in Example 23 was conducted to form a pattern. Nopattern was formed.

EXAMPLE 24

15 wt % of cyclohexanone solution of adamantylmethacrylate-3-oxocyclohexyl methacrylate copolymer expressed by thefollowing structural formula

and having a 41:59 composition ratio, a 13900 weight-averaged molecularweight, and a 1.51 degree of dispersion was prepared. To this solution,1 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added to the polymer to prepare a resist solution. This solution wasapplied by spin coating to a wafer coated with hard-baked novolak resin,and baked for 100 seconds on a hot plate of 100° C. And a 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by an ArF excimerstepper (NA=0.55), and then subjected to PEB at 150° C. for 60 seconds.Subsequently the resist film was immersed in mixed liquid of 2.38% ofTMAH aqueous solution and isopropyl alcohol by a 1:1 volume ratio fordevelopment. A 0.2 μm-wide L & S pattern was resolved at a 25 mJ/cm²radiation dose.

EXAMPLE 25

15 wt % of cyclohexanone solution of adamantylmethacrylate-3-oxocyclohexyl methacrylate copolymer expressed by thefollowing structural formula

and having a 41:59 composition ratio, a 13900 weight-averaged molecularweight, and a 1.51 degree of dispersion was prepared. To this solution,2 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added as an acid generating substance to the polymer to prepare aresist solution. This solution was applied by spin coating to a wafercoated with hard-baked novolak resin, and baked for 100 seconds on a hotplate of 100° C. And a 0.4 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by an ArF excimerstepper (NA=0.55), and then subjected to PEB at 150° C. for 60 seconds.Subsequently the resist film was immersed in mixed liquid of 2.38% ofTMAH aqueous solution and isopropyl alcohol by a 1:1 volume ratio fordevelopment. A 0.2 μm-wide L & S pattern was resolved at a 12 mJ/cm²radiation dose.

EXAMPLE 26

2-norbornyl methacrylate monomer, t-butyl methacrylate monomer, andmethacrylic acid were loaded in a ratio of 2:1:1. 0.5 mol/l of asolvent, 1,4-dioxane and 20 mol % of a polymerization initiator AIBNwere added, and polymerization took place for about 9 hours at 80° C.After the polymerization, precipitation purification was conducted withn-hexane. And the terpolymer expressed by the following structuralformula

and having a composition ratio of 56:31:13 and a 5833 weight-averagemolecular weight and 2.34 degree of dispersion was prepared.

Then to the thus-synthesized polymer, 15 wt % of triphenylsulfoniumhexafluoroantimonate as an acid generating substance expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied onto a wafer coated with hard-baked novolak resin, in a 0.7μm-thickness by spin coating, and the wafer was prebaked on a hot plateat 60° C. for 100 seconds.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, analkali aqueous solution, and then rinsed with deionized water for 30seconds. The threshold energy Eth of the radiation dose for thisexposure was 63 mJ/cm². A minimum resolution was a 0.35 μm-wide L & Spattern.

EXAMPLE 27

Di-t-butyl itaconate monomer and cyclohexyl methacrylate monomer wereloaded in a 3:1 ration, and 20 mol % of MAIB was added. Then bulkpolymerization took place at 80° C. for about 10.5 hours. The bulkpolymerization was followed by precipitation purification with methanol.And the copolymer expressed by the following structural formula

and having a 52:48 composition ratio, a 6923 weight-average molecularweight and a 2.12 degree of dispersion was prepared.

Then to the thus-synthesized polymer, 15 wt % of triphenylsulfoniumhexafluoroantimonate as an acid generating substance expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied onto an HMDS treated wafer in a 0.7 μm-thickness by spincoating, and the wafer was prebaked on a hot plate at 60° C. for 100seconds.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, analkali aqueous solution, and then rinsed with deionized water for 30seconds. The threshold energy Eth of the radiation dose for thisexposure was 9.52 mJ/cm². A minimum resolution was a 0.5 μm-wide L & Spattern.

EXAMPLE 28

A 15 wt % cyclohexanone solution of tricyclo[5.2.1.0^(2.6)] decanylmethacrylate-3-oxocyclohexyl methacrylate copolymer expressed by thefollowing structural formula

and having a 50:50 composition ratio, a 13900 weight-average molecularweight and a 1.41 dispersion ration was prepared.

Triphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added to the solution by 10 wt % to the copolymer, and a resistsolution was prepared. This resist solution was applied to an HMDStreated Si wafer by spin coating, and the wafer was baked for 100seconds on a hot plate at 100° C., and a 0.7 μm-thickness resist filmwas formed.

The thus-coated resist film on the wafer was exposed by a krF excimerstepper and was subjected to PEB at 150° C. for 60 seconds. Then thewafer was immersed into a volume ratio 3:1 mixed liquid of a 2.38% TMAHaqueous solution and isopropyl alcohol for development. At a 23 mJ/cm²radiation dose, a 0.45 μm-wide L & S pattern was formed.

EXAMPLE 29

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance tovinylphenol-adamantyloxycarbonylmethyl styrene-tert-butyl methacrylateterpolymer expressed by the following structural formula

and having a 50:20:30 composition ratio, and an 18 wt % ethyl lactatesolution was prepared. This solution was applied onto an Si wafer byspin coating and baked for 90 seconds on a hot plate at 110° C. A 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 26 mJ/cm² radiationdose. When PEB was conducted after the resist was left for 30 minutesafter the exposure, a 0.275 μm-wide L & S pattern was resolved at thesame radiation dose.

EXAMPLE 30

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance tovinylphenol-norbornyloxycarbonylmethyl styrene-tert-butyl methacrylateterpolymer expressed by the following structural formula

and having a 50:30:30 composition ratio, and an 18 wt % ethyl lactatesolution was prepared. This solution was applied onto an Si wafer byspin coating and baked for 90 seconds on a hot plate at 110° C. A 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 22 mJ/cm radiation dose.When PEB was conducted after the resist was left for 30 minutes afterthe exposure, a 0.275 μm-wide L & S pattern was resolved at the sameradiation dose.

EXAMPLE 31

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance to vinylphenol-tert-butylmethacrylate copolymer (produced by Maruzen Sekiyu) expressed by thefollowing structural formula

and having a 60:40 composition ratio, and 1-adamantane carboxylatet-butyl expressed by the following formula

was also added by the same weight % as that of the copolymer, and an 18wt % ethyl lactate solution was prepared. This solution was applied ontoan Si wafer by spin coating and baked for 90 seconds on a hot plate at110° C. A 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 8.5 mJ/cm² radiationdose. When PEB was conducted after the resist was left for 30 minutesafter the exposure, a 0.275 μm-wide L & S pattern was resolved at thesame radiation dose.

The threshold energy Eth of the radiation dose when PEB was conductedimmediately after the exposure was 5.5 mJ/cm². The Eth did notsubstantially change after post exposure 30 minutes delay.

EXAMPLE 32

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance to vinylphenol-tert-butylmethacrylate copolymer (produced by Maruzen Sekiyu) expressed by thefollowing structural formula

and having a 60:40 composition ratio, and di-t-butyl fumarate expressedby the following formula

was also added by the same weight % as that of the copolymer, and an 18wt % ethyl lactate solution was prepared. This solution was applied ontoan Si wafer by spin coating and baked for 90 seconds on a hot plate at110° C. A 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 12 mJ/cm² radiationdose. When PEB was conducted after the resist was left for 30 minutesafter the exposure, a 0.275 μm-wide L & S pattern was resolved at thesame radiation dose.

The threshold energy Eth of the radiation dose when PEB was conductedimmediately after the exposure was 8 mJ/cm². The Eth did notsubstantially change after post exposure 30 minutes delay.

EXAMPLE 33

5 wt % of diphenyliodonium triflate expressed by the followingstructural formula

was added as an acid generating substance to vinylphenol-tert-butylmethacrylate copolymer (produced by Maruzen Sekiyu) expressed by thefollowing structural formula

and having a 50:50 composition ratio, and di-t-butyl fumarate expressedby the following formula

was also added by the same weight % as that of the copolymer, and an 18wt % ethyl lactate solution was prepared. This solution was applied ontoan Si wafer by spin coating and baked for 90 seconds on a hot plate at110° C. A 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 18 mJ/cm² radiationdose. When PEB was conducted after the resist was left for 30 minutesafter the exposure, a 0.275 μm-wide L & S pattern was resolved with atsame radiation dose.

The threshold energy Eth of the radiation dose when PEB was conductedimmediately after the exposure was 8 mJ/cm². The Eth did notsubstantially change after post exposure 30 minutes delay.

EXAMPLE 34

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance tovinylphenol-tert-butoxycarbonyloxystyrene copolymer (produced by MaruzenSekiyu) expressed by the following structural formula

and having a 70:30 composition ratio, and 1-adamantane carboxylatet-butyl expressed by the following formula

was also added by the same weight % as that of the copolymer, and an 18wt % ethyl lactate solution was prepared. This solution was applied ontoan Si wafer by spin coating and baked for 90 seconds on a hot plate at110° C. A 0.7 μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 35 mJ/cm² radiationdose. When PEB was conducted after the resist was left for 30 minutesafter the exposure, a 0.275 μm-wide L & S pattern was resolved with atsame radiation dose.

[Control 16]

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance to vinylphenol-tert-butylmethacrylate copolymer (produced by Maruzen Sekiyu) expressed by thefollowing structural formula

and having a 50:50 composition ratio, and an 18 wt % ethyl lactatesolution was prepared. This solution was applied onto an Si wafer byspin coating and baked for 90 seconds on a hot plate at 110° C. A 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 13 mJ/cm² radiationdose. When PEB was conducted for 60 seconds at 90° C. after the resistwas left for 5 minutes after the exposure, the surface became insoluble,and a 0.275 μm-wide L & S pattern could not be resolved at the sameradiation dose.

[Control 17]

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance to vinylphenol-tert-butylmethacrylate copolymer (produced by Maruzen Sekiyu) expressed by thefollowing structural formula

and having a 60:40 composition ratio, and an 18 wt % ethyl lactatesolution was prepared. This solution was applied onto an Si wafer byspin coating and baked for 90 seconds on a hot plate at 110° C. A 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.3 μm-wide L & S pattern was resolved at an 8 mJ/cm² radiation dose.When PEB was conducted for 60 seconds at 90° C. after the resist wasleft for 10 minutes after the exposure, the surface became insoluble,and a 0.3 μm-wide L & S pattern could not be resolved at the sameradiation dose.

The threshold energy Eth of the radiation dose when PEB was conductedimmediately after the exposure was 5.5 mJ/cm², but the Eth in the caseof the resist was 10 mJ/cm² after post exposure 30 minutes delay.

[Control 18]

5 wt % of triphenylsulfonium triflate expressed by the followingstructural formula

was added as an acid generating substance tovinylphenol-tert-butoxycarbonyloxystyrene copolymer expressed by thefollowing structural formula

and having a 70:30 composition ratio, and an 18 wt % ethyl lactatesolution was prepared. This solution was applied onto an Si wafer byspin coating and baked for 90 seconds on a hot plate at 110° C. A 0.7μm-thickness resist film was formed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 90° C. for 60 seconds. Then theresist film was developed with a 2.38% TMAH aqueous solution for 1minute.

A 0.275 μm-wide L & S pattern was resolved at a 30 mJ/cm² radiationdose. When PEB was conducted for 60 seconds at 90° C. after the resistwas left for 10 minutes after the exposure, the surface becameinsoluble, and a 0.275 μm-wide L & S pattern could not be resolved atthe same radiation dose.

EXAMPLE 35

t-butyl methacrylate monomer and itaconic anhydride monomer were loadedin a ratio of 1:1, and a 2 mol/l solution of 1,4-dioxane solution wasprepared. Then 5 mol % of AIBN was added to the solution. Thenpolymerization took place for about 10 hours at 80° C. After thepolymerization precipitation purification was conducted with n-hexane.The copolymer expressed by the following structural formula

and having a 63:37 composition ratio, a 6500 weigh-average molecularweight and a 2.23 degree of dispersion was prepared.

Then to the thus-synthesized polymer, 15 wt % of triphenylsulfoniumhexafluoroantimonate as an acid generating substance expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied onto a silicon wafer in a 0.7 μm-thickness by spin coating, andthe wafer was prebaked on a hot plate at 100° C. for 100 seconds.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution and water (volume ratio;NMD-3:water=1:5), and then rinsed with deionized water for 30 seconds.The threshold energy Eth of the radiation dose for this exposure was 17mJ/cm². A minimum resolution was a 0.275 μm-wide L & S pattern. Nopattern peeling or falls were observed.

When, in place of the 1:5 volume ratio solution of NMD-3 and water, avolume ratio 1:10 solution of NMD-3 and water and a 1:20 volume ratiosolution of NMD-3 and water were used, the same results were obtained.

[Control 19]

A 2 mol % 1,4-dioxane solution of t-butyl methacrylate monomer wasprepared, and 5 mol % of AIBN was added as a polymerization initiator.Polymerization took place for about 10 hours at 80° C. Following thepolymerization, precipitation purification was conducted with a solutionof methanol and water (methanol:water=3:1). And the polymer expressed bythe following structural formula

and having a 10097 weight-average molecular weight and a 1.88 degree ofdispersion was prepared.

Then 15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing formula

was added to the thus-synthesized polymer as an acid generatingsubstance, and a cyclohexanone solution was prepared. This solution wasapplied onto a silicon wafer in a 0.7 μm-thickness by spin coating andwas prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution), and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 17 mJ/cm². A minimum resolution was a 0.35 μm-wide L & Spattern with 56 mJ/cm². L & S patterns below 0.35 μm-wide peeled andvanished.

When a 1:5 volume ratio solution of NMD-3 and water was used as adeveloper in place of NMD-3, the threshold value energy Eth of theradiation dose was 16.1 mJ/cm². A minimum resolution was a 0.3 μm-wide L& S pattern with 56 mJ/cm². L & S patterns below 0.3 μm-wide peeled andvanished.

EXAMPLE 36

Adamantyl methacrylate monomer, t-butyl acrylate monomer and itaconicanhydride monomer were loaded by 4:2:4, and a 1 mol/l 1,4-dioxanesolution was prepared. 10 mol % of AIBN as a polymerization initiatorwas added to the solution. Then polymerization took place for about 8hours at 80° C. Following the polymerization, precipitation purificationwas conducted with methanol. The copolymer expressed by the followingstructural formula

and having a 58:14:28 composition ratio, a 13000 weight-averagemolecular weight and a 1.81 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 17 mJ/cm². A minimum resolution was a 0.25 μm-wide L & Spattern with 50 mJ/cm². No pattern peeling or falls were observed.

When PEB was subjected at 100° C. for 100 seconds, and a 5:1 volumeratio solution of NMD-3 and isopropyl alcohol was used as a developer inplace of NMD-3, the threshold value energy Eth of the radiation dose was25.5 mJ/cm². A minimum resolution was a 0.275 μm-wide L & S pattern with44 mJ/cm². No pattern peeling or falls were observed.

[Control 20]

Adamantyl methacrylate monomer and t-butyl acrylate monomer were loadedby 1:1, and a 5 mol/l toluene solution was prepared. 20 mol % of AIBN asa polymerization initiator was added to the solution. Thenpolymerization took place for about 8 hours at 80° C. Following thepolymerization, precipitation purification was conducted with methanol.The copolymer expressed by the following structural formula

and having a 58:42 composition ratio, a 5100 weight-average molecularweight and a 1.43 degree of dispersion was prepared. The glasstransition temperature of this polymer was 126° C. by thermal analysis.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 50 mJ/cm². A minimum resolution was a 0.45 μm-wide L & Spattern with 30 mJ/cm². Resist residues between patterns were striking,and pattern peeling or falls were observed.

EXAMPLE 37

Dimethyladamantyl methacrylate monomer, t-butyl acrylate monomer anditaconic anhydride monomer were loaded by 4:2:4, and a 1 mol/l1,4-dioxane solution was prepared. 10 mol % of AIBN as a polymerizationinitiator was added to the solution. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 58:14:28 composition ratio, a 13000 weight-averagemolecular weight and a 1.81 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 17 mJ/cm². A minimum resolution was a 0.25 μm-wide L & Spattern with 50 mJ/cm². No pattern peeling or falls were observed.

EXAMPLE 38

Adamantyl methacrylate monomer, t-butyl α-chloroacrylate monomer anditaconic anhydride monomer were loaded by 4:2:4, and a 1 mol/l1,4-dioxane solution was prepared. 10 mol % of AIBN as a polymerizationinitiator was added to the solution. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 58:14:28 composition ratio, a 13000 weight-averagemolecular weight and a 1.81 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 17 mJ/cm². A minimum resolution was a 0.25 μm-wide L & Spattern with 50 mJ/cm². No pattern peeling or falls were observed.

[Control 21]

Adamantyl methacrylate monomer and t-butyl α-chloroacrylate monomer wereloaded by 1:1, and a 5 mol/l toluene solution was prepared. 10 mol % ofAIBN as a polymerization initiator was added to the solution. Thenpolymerization took place for about 8 hours at 80° C. Following thepolymerization, precipitation purification was conducted with methanol.The copolymer expressed by the following structural formula

and having a 58:42 composition ratio, a 5100 weight-average molecularweight and a 1.43 degree of dispersion was prepared. The glasstransition temperature of this polymer was 126° C.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds.

Serious pattern peeling took place, and a minimum resolution was a 0.5μm-wide L & S pattern.

EXAMPLE 39

Adamantyl methacrylate monomer, α,α-dimethylbenzyl methacrylate monomer,and itaconic anhydride monomer were loaded by 4:2:4, and a 1 mol/l1,4-dioxane solution was prepared. 10 mol % of AIBN as a polymerizationinitiator was added to the solution. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 56:11:33 composition ratio, a 16000 weight-averagemolecular weight and a 1.91 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 8 mJ/cm². A minimum resolution was a 0.275 μm-wide L & Spattern with 23 mJ/cm². No pattern peeling or falls were observed.

EXAMPLE 40

Adamantyl methacrylate monomer, 3-oxocyclohexyl methacrylate monomer,and itaconic anhydride monomer were loaded by 4:2:4, and a 1 mol/l1,4-dioxane solution was prepared. 10 mol % of AIBN as a polymerizationinitiator was added to the solution. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 65:15:20 composition ratio, a 13200 weight-averagemolecular weight and a 1.92 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 19.2 mJ/cm². A minimum resolution was a 0.25 μm-wide L & Spattern with 54 mJ/cm². No pattern peeling or falls were observed.

[Control 22]

Adamantyl methacrylate monomer, 3-oxocyclohexyl methacrylate monomerwere loaded by 1:1, and a 5 mol/l toluene solution was prepared. 20 mol% of AIBN as a polymerization initiator was added to the solution. Thenpolymerization took place for about 8 hours at 80° C. Following thepolymerization, precipitation purification was conducted with methanol.The copolymer expressed by the following structural formula

and having a 65:35 composition ratio, a 14400 weight-average molecularweight and a 1.53 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 60.2 mJ/cm². A minimum resolution was a 0.4 μm-wide L & Spattern with 208 mJ/cm². Much pattern peeling took place.

EXAMPLE 41

Adamantyl methacrylate monomer, tetrahydropyranyl methacrylate monomer,and itaconic anhydride monomer were loaded by 4:2:4, and a 1 mol/l1,4-dioxane solution was prepared. 10 mol % of AIBN as a polymerizationinitiator was added to the solution. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 57:14:29 composition ratio, a 36200 weight-averagemolecular weight and a 2.14 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed-by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy Eth of the radiation dose for thisexposure was 42.2 mJ/cm². A minimum resolution was a 0.30 μm-wide L & Spattern with 141 mJ/cm². No pattern peeling or falls were observed.

[Control 23]

Adamantyl methacrylate monomer, tetrahydropyranyl methacrylate monomerwere loaded by 1:1, and a 5 mol/l toluene solution was prepared. 20 mol% of AIBN as a polymerization initiator was added to the solution. Thenpolymerization took place for about 8 hours at 80° C. Following thepolymerization, precipitation purification was conducted with methanol.The copolymer expressed by the following structural formula

and having a 58:42 composition ratio, a 23000 weight-average molecularweight and a 1.90 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. No pattern could be formed.

EXAMPLE 42

Adamantyl methacrylate monomer, t-butoxystyrene monomer and itaconicanhydride monomer were loaded by 4:2:4, and a 1 mol/l 1,4-dioxanesolution was prepared. 10 mol % of AIBN as a polymerization initiatorwas added to the solution. Then polymerization took place for about 8hours at 80° C. Following the polymerization, precipitation purificationwas conducted with methanol. The terpolymer expressed by the followingstructural formula

and having a 21:36:43 composition ratio, a 8200 weight-average molecularweight and a 1.95 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. No pattern peeling or falls were observed.

EXAMPLE 43

Adamantyl methacrylate monomer, t-BOC styrene monomer and itaconicanhydride monomer were loaded by a 4:2:4 ratio, and a 1 mol/l1,4-dioxane solution was prepared. 10 mol % of AIBN as a polymerizationinitiator was added to the solution. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with methanol. The terpolymer expressed bythe following structural formula

and having a 21:36:43 composition ratio, a 8200 weight-average molecularweight and a 1.95 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film one the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. No pattern peeling or falls were observed.

EXAMPLE 44

Itaconic anhydride monomer and di-t-butyl itaconate monomer were loadedin a 2:3 ratio, and 20 mol % of dimethyl 2,2-azoisobisbutyrate was addedas a polymerization initiator. Then, bulk polymerization took place forabout 3 hours at 80° C. After e polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 23:77 composition ratio, a 6357 weight-average molecularweight and 2.34 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy of the radiation dose was 12.6mJ/cm². A minimum resolution was a 0.3 μm-wide L & S pattern with 38mJ/cm². No pattern peeling or falls were observed.

EXAMPLE 45

Itaconic anhydride monomer and di-t-butyl fumarate monomer were loadedin a 2:3 ratio, and 20 mol % of dimethyl 2,2-azoisobisbutyrate was addedas a polymerization initiator. Then, bulk polymerization took place forabout 3 hours at 80° C. After e polymerization, precipitationpurification was conducted with methanol. The copolymer expressed by thefollowing structural formula

and having a 23:77 composition ration, a 6357 weight-average molecularweight and 2.34 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 60° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a solution ofNMD-3, an alkali aqueous solution, and then rinsed with deionized waterfor 30 seconds. The threshold energy of the radiation dose was 12.6mJ/cm². A minimum resolution was a 0.3 μm-wide L & S pattern with 38mJ/cm². No pattern peeling or falls were observed.

EXAMPLE 46

Methacrylonitrile monomer, t-butyl methacrylate monomer and itaconicanhydride monomer were loaded by 4:2:4, and a 5 mol/l 1,4-dioxanesolution was prepared. 1 mol % of AIBN as a polymerization initiator wasadded to the solution. Then polymerization took place for about 8 hoursat 80° C. Following the polymerization, precipitation purification wasconducted with n-hexane. The terpolymer expressed by the followingstructural formula

and having a 41:21:38 composition ratio, a 26400 weight-averagemolecular weight and a 1.87 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a 2.3% TMAHaqueous solution. A 0.3 μm-wide L & S pattern was resolved at a 41mJ/cm² radiation dose.

[Control 24]

Methacrylonitrile monomer and t-butyl methacrylate monomer were loadedby 1:1, and a 5 mol/l 1,4-dioxane solution and 1 mol % of AIBN, apolymerization initiator were added. Then polymerization took place forabout 8 hours at 80° C. Following the polymerization, precipitationpurification was conducted with a mixed solution of methanol and water(methanol:water=2:1). The copolymer expressed by the followingstructural formula

and having a 41:59 composition ratio, a 16400 weight-average molecularweight and a 1.77 degree of dispersion was prepared.

13 wt % of cyclohexanone solution of this copolymer was prepared, andtriphenylsulfonium hexafluoroantimonate expressed by the followingstructural formula

was added to this solution as a substance generating substance by 15 wt% to the polymer, and a resist solution was prepared. This solution wasapplied onto a silicon wafer by spin coating and prebaked for 100seconds on a hot plate at 100° C. And a 0.7 μm-thickness thin film wasformed.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 100° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with a 2.38% TMAHaqueous solution. A 0.3 μm-wide L & S pattern was resolved at a 70mJ/cm² radiation dose, but in comparison with that of the case withoutmethacrylonitrile (Control 19), the sensitivity was lower.

EXAMPLE 47

Methyl α-cyanoacrylate monomer, t-butyl methacrylate monomer anditaconic anhydride were loaded by 4:2:4, and a 1 mol/l 1,4-dioxanesolution was prepared. 10 mol % of AIBN as a polymerization initiatorwas added to the solution. Then polymerization took place for about 8hours at 80° C. Following the polymerization, precipitation purificationwas conducted with methanol. The terpolymer expressed by the followingstructural formula

and having a 58:14:28 composition ratio, a 13000 weight-averagemolecular weight and a 1.81 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added, and a cyclohexanone solution was prepared. This solution wasapplied to a silicon wafer in a 0.7 μm-thickness by spin coating, andthen prebaked for 100 seconds on a hot plate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, analkali aqueous solution and rinsed for 30 seconds with deionized water.The threshold energy of the radiation dose was 17 mJ/cm². A minimumresolution was a 0.25 μm-wide L & S pattern with 50 mJ/cm². No patternpeeling or falls were observed.

EXAMPLE 48

Adamantyl methacrylate monomer, t-amyl methacrylate monomer and itaconicanhydride were loaded by 4:2:4, and a 1 mol/l 1,4-dioxane solution wasprepared. 10 mol % of AIBN as a polymerization initiator was added tothe solution. Then polymerization took place for about 8 hours at 80° C.Following the polymerization, precipitation purification was conductedwith methanol. The copolymer expressed by the following structuralformula

and having a 58:14:28 composition ratio, a 13000 weight-averagemolecular weight and a 1.81 degree of dispersion was prepared.

15 wt % of triphenylsulfonium hexafluoroantimonate expressed by thefollowing structural formula

was added to the thus-synthesized polymer, and a cyclohexanone solutionwas prepared. This solution was applied to a silicon wafer in a 0.7μm-thickness by spin coating, and then prebaked for 100 seconds on a hotplate at 100° C.

The thus-prepared resist film on the wafer was exposed by a KrF excimerstepper and then subjected to PEB at 130° C. for 60 seconds.Subsequently the resist was developed for 60 seconds with NMD-3, analkali aqueous solution and rinsed for 30 seconds with deionized water.The threshold energy of the radiation dose was 17 mJ/cm². A minimumresolution was a 0.25 μm-wide L & S pattern with 50 mJ/cm². No patternpeeling or falls were observed.

EXAMPLE 49

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-adamantyl methacrylate copolymer expressed by the followingstructural formula

and having a 50:50 composition ratio was prepared.

Triphenylsulfonium hexafluoroantimonate was added to the solution by 2wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to a Si wafer by spin coating, and thewafer was baked for 100 seconds on a hot plate at 100° C., and a 0.7μm-thickness resist film was formed. A solution of 5 wt % of polyolefineresin in t-butylcyclohexane was applied onto the wafer by spin coatingand baked for 100 seconds on a hot plate at 100° C., and a 0.2μm-thickness protecting film was formed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 100° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was removed.

Then the wafer was immersed into a 2.38% TMAH solution for development.

A 0.45 μm-wide L & S pattern was resolved at a 210 mJ/cm² radiationdose.

[Control 25]

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-adamantyl methacrylate copolymer expressed by the followingstructural formula

and having a 50:50 composition ratio was prepared.

Triphenylsulfonium hexafluoroantimonate was added to the solution by 2wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was baked for 100 seconds on a hot plate at 100°C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in heptane was applied ontothe wafer by spin coating. The solution did not homogeneously spreadover the wafer, and a protecting film could not be applied.

[Control 26]

A 15 wt % cyclohexanone solution of poly adamantyl-methacrylateexpressed by the following structural formula

was prepared.

This solution was applied to an HMDS treated Si wafer by spin coating,and the wafer was baked for 100 seconds on a hot plate at 100° C., and a0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in t-butylcyclohexane wasapplied onto the wafer by spin coating,-then the thin film of polyadamantylmethacrylate was resolved.

[Control 27]

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-adamantyl methacrylate expressed by the followingstructural formula

and having a 50:50 composition ratio was prepared. 2 wt % oftriphenylsulfonium hexafluoroantimonate as an acid generating substancewas added to this solution, and a resist solution was prepared.

This solution was applied to an HMDS treated Si wafer by spin coating,and the wafer was baked for 100 seconds on a hot plate at 100° C., and a0.7 μm-thickness resist film was formed.

The resist thin film was exposed by a KrF stepper without applying aprotecting film on the wafer, and then subjected to PEB for 60 secondsat 150° C.

Then the resist film was developed with a 2.38 TMAH aqueous solution.

An unresolved layer was generated on the surface of the resist thinfilm, and no pattern could be resolved at a 300 mJ/cm² radiation dose.

EXAMPLE 50

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-adamantyl methacrylate copolymer expressed by the followingstructural formula

and having a 45:55 composition ratio was prepared.

Triphenylsulfonium hexafluoroantimonate as an acid generating substancewas added to the solution by 2 wt % to the copolymer, and a resistsolution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was baked for 100 seconds on a hot plate at 100°C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in 1,5-cyclooctadieneexpressed by the following structural formula

was applied onto the wafer by spin coating and baked for 100 seconds ona hot plate at 100° C., and a 0.2 μm-thickness protecting. film wasformed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 150° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was removed.

Then the wafer was immersed for 60 seconds in a 8:1 volume ratio-mixedsolution of 2.38% TMAH aqueous solution and isopropyl alcohol fordevelopment.

A 0.275 μm-wide L & S pattern was resolved at a 70 mJ/cm² radiationdose.

[Control 28]

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-adamantyl methacrylate copolymer expressed by the followingstructural formula

and having a 45:55 composition ratio was prepared.

Triphenylsulfonium hexafluoroantimonate as an acid generating substancewas added to the solution by 2 wt % to the copolymer, and a resistsolution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was baked for 100 seconds on a hot plate at 100°C., and a 0.7 μm-thickness resist film was formed.

The resist film was exposed by a KrF stepper without application of aprotecting film, and then subjected to PEB for 60 seconds at 150° C.

Then, the wafer was immersed in a 8:1 volume ratio mixed solution of aTMAH aqueous solution and isopropyl alcohol for 60 seconds fordevelopment.

Even with the radiation dose increased up to 100 mJ/cm², only a 0.35μm-wide L & S pattern was resolved.

EXAMPLE 51

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-dimethyladamantyl methacrylate copolymer expressed by thefollowing structural formula

and having a 45:55 composition ratio was prepared.

Triphenylsulfonium hexafluoroantimonate as an acid generating substancewas added to the solution by 5 wt % to the copolymer, and a resistsolution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polydiene resin in limonene expressed by thefollowing structural formula

was applied onto the wafer by spin coating and baked for 100 seconds ona hot plate at 100° C., and a 0.2 μm-thickness protecting film wasformed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 150° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was removed.

Then the wafer was immersed for 60 seconds in a 3:1 volume ratio-mixedsolution of 2.38% TMAH aqueous solution and isopropyl alcohol fordevelopment.

A 0.25 μm-wide L & S pattern was resolved at an 18 mJ/cm² radiationdose.

[Control 29]

A 15 wt % cyclohexanone solution of 3-oxocyclohexylmethacrylate-dimethyladamantyl methacrylate copolymer expressed by thefollowing structural formula

and having a 45:55 composition ratio was prepared.

Triphenylsulfonium hexafluoroantimonate as an acid generating substancewas added to the solution by 5 wt % to the copolymer, and a resistsolution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper without application of a protecting film and was subjected toPEB at 150° C. for 60 seconds.

Then the wafer was immersed for 60 seconds in a 3:1 volume ratio-mixedsolution of 2.38% TMAH aqueous solution and isopropyl alcohol fordevelopment.

A 0.25 μm-wide L & S pattern was resolved at an 18 mJ/cm² radiationdose, but the pattern was a much thinner line pattern than desired.

EXAMPLE 52

A 15 wt % cyclohexanone solution of t-butyl methacrylate-adamantylacrylate-methacrylic acid terpolymer expressed by the followingstructural formula

and having a 40:40:20 composition ratio was prepared. Triphenylsulfoniumhexafluoroantimonate as an acid generating substance was added to thesolution by 2 wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in p-cymene was applied ontothe wafer by spin coating and baked for 100 seconds on a hot plate at100° C., and a 0.2 μm-thickness protecting film was formed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 150° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was removed.

Then the wafer was immersed for 60 seconds in a 2.38% TMAH aqueoussolution for development.

A 0.3 μm-wide L & S pattern was resolved at a 35 mJ/cm² radiation dose.

[Control 30]

A 15 wt % cyclohexanone solution of t-butyl methacrylate-adamantylacrylate copolymer expressed by the following structural formula

and having a 50:50 composition ratio was prepared. Triphenylsulfoniumhexafluoroantimonate as an acid generating substance was added to thesolution by 2 wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in p-cymene was applied ontothe wafer by spin coating, then the resist thin film was resolved.

[Control 31]

A 15 wt % cyclohexanone solution of t-butyl methacrylate-adamantylacrylate-methacrylic acid terpolymer expressed by the followingstructural formula

and having a 40:40:20 composition ratio was prepared. Triphenylsulfoniumhexafluoroantimonate as an acid generating substance was added to thesolution by 2 wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in xylene was applied onto thewafer by spin coating, then the resist film was resolved.

EXAMPLE 53

A 15 wt % cyclohexanone solution of t-butyl methacrylate-norbornylmethacrylate-hydroxyethyl methacrylate terpolymer expressed by thefollowing structural formula

and having a 30:40:30 composition ratio was prepared. Triphenylsulfoniumhexafluoroantimonate as an acid generating substance was added to thesolution by 5 wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polydiene resin in 1-decene expressed by thefollowing structural formulaCH₂═CH

CH₂

₇CH₃was applied onto the wafer by spin coating and baked for 100 seconds ona hot plate at 100° C., and a 0.2 μm-thickness protecting film wasformed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 150° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was stripped.

Then the wafer was immersed for 60 seconds in a 2.38% TMAH aqueoussolution for development.

A 0.3 μm-wide L & S pattern was resolved at a 40 mJ/cm² radiation dose.

[Control 32]

A 15 wt % cyclohexanone solution of t-butyl methacrylate-norbornylmethacrylate copolymer expressed by the following structural formula

and having a 45:55 composition ratio was prepared. Triphenylsulfoniumhexafluoroantimonate as an acid generating substance was added to thesolution by 2 wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polydiene resin in 1-decene expressed by thefollowing structural formulaCH₂═CH

CH₂

₇CH₃was applied onto the wafer by spin coating, and the resist film wasresolved.

[Control 33]

A 15 wt % cyclohexanone solution of t-butyl methacrylate-norbornylmethacrylate-hydroxyethyl methacrylate terpolymer expressed by thefollowing structural formula

and having a 30:40:30 composition ratio was prepared. Triphenylsulfoniumhexafluoroantimonate as an acid generating substance was added to thesolution by 5 wt % to the copolymer, and a resist solution was prepared.

This resist solution was applied to an HMDS treated Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper without application of a protecting film and was subjected toPEB at 150° C. for 60 seconds.

Then the wafer was immersed for 60 seconds in a 2.38% TMAH aqueoussolution for development.

An unsolved layer was generated on the surface of the resist, and nopattern could be resolved.

EXAMPLE 54

15 wt % of triphenylsulfonium hexafluoroantimonate as an acid generatingsubstance was added to adamantyl methacrylate-t-butyl acrylate-itaconicanhydride terpolymer expressed by the following structural formula.

and having a 58:14:28 composition ratio, and a cyclohexanone solutionwas prepared. This resist solution was applied to a Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in t-butylcyclohexaneexpressed by the following structural formula

was applied onto the wafer by spin coating and baked for 100 seconds ona hot plate at 100° C., and a 0.2 μm-thickness protecting film wasformed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 100° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was removed.

Then the resist film was developed for 60 seconds with NMD-3, an alkaliaqueous solution and rinsed for 30 seconds with deionized water. Thethreshold energy of the radiation dose was 13 mJ/cm². A 0.25 μm-wide L &S pattern was resolved at 41 mJ/cm².

[Control 34]

15 wt % of triphenylsulfonium hexafluoroantimonate as an acid generatingsubstance was added to adamantyl methacrylate-t-butyl acrylate copolymerexpressed by the following structural formula

and having a 58:42 composition ratio, and a cyclohexanone solution wasprepared. This resist solution was applied to a Si wafer by spincoating, and the wafer was prebaked for 100 seconds on a hot plate at100° C., and a 0.7 μm-thickness resist film was formed.

A solution of 5 wt % of polyolefine resin in t-butylcyclohexaneexpressed by the following structural formula

was applied onto the wafer by spin coating, and the resist thin filmbecame opaque.

[Control 35]

A 15 wt % of triphenylsulfonium hexafluoroantimonate as an acidgenerating substance was added to adamantyl methacrylate-t-butylmethacrylate-itaconic anhydride terpolymer expressed by the followingstructural formula

and having a 58:14:28 composition ratio and a cyclohexanone solution wasprepared. This resist solution was applied to a Si wafer in a 7μm-thickness by spin coating and prebaked for 100 seconds on a hot plateat 100° C.

A solution of 5 wt % of polyolefine resin in xylene was applied onto thewafer by spin coating, and the resist thin film was resolved.

Toluene and ethylene benzene were used as coating solvents in place ofxylene, and similarly the resist thin films were resolved.

EXAMPLE 55

15 wt % of triphenylsulfonium hexafluoroantimonate as an acid generatingsubstance was added to adamantyl methacrylate-t-butyl acrylate-itaconicanhydride terpolymer expressed by the following structural formula

and having a 58:14:28 composition ratio, and a cyclohexanone solutionwas prepared. This resist solution was applied to a Si wafer in a 0.7μm-thickness by spin coating, and prebaked for 100 seconds on a hotplate at 100° C.

A solution of 5 wt % of polyolefine resin in limonene expressed by thefollowing structural formula

was applied onto the wafer by spin coating and baked for 100 seconds ona hot plate at 100° C., and a 0.2 μm-thickness protecting film wasformed.

The thus-coated resist film on the wafer was exposed by a KrF excimerstepper and was subjected to PEB at 100° C. for 60 seconds. Thencyclohexane was applied onto the wafer by spin coating, and theprotecting film was removed.

Then the resist film was developed for 60 seconds with NMD-3, an alkaliaqueous solution and rinsed for 30 seconds with deionized water. Thethreshold energy of the radiation dose was 13 mJ/cm². A 0.25 μm-wide L &S pattern was resolved at 41 mJ/cm².

The same resolving power was obtained by using as a coating solvent, inplace of limonene, 1,5-cyclooctadiene expressed by the followingstructural formula

or using, 1-decene expressed by the following structural formulaCH₂═CH

CH₂

₇CH₃

[Control 36]

15 wt % of triphenylsulfonium hexafluoroantimonate as an acid generatingsubstance was added to adamantyl methacrylate-t-butyl acrylate-itaconicanhydride terpolymer expressed by the following structural formula

and having a 58:14:28 composition ratio, and a cyclohexanone solutionwas prepared. This resist solution was applied to a Si wafer in a 0.7μm-thickness by spin coating, and prebaked for 100 seconds on a hotplate at 100° C.

A solution of 5 wt % of polyolefine resin in methylcyclohexane wasapplied onto the wafer by spin coating, and the solution did notuniformly spread over the wafer without forming a protecting film.

1-12. (canceled)
 13. A radiation sensitive material comprising: acopolymer including a unit structure expressed by

 (where X₁ and X₂ represent —C(CH₃)₂R₁,

 and  R₁ represents alkyl group); and a unit structure generating analkali soluble group in the presence of an acid; and a substancegenerating an acid by application of radiation.
 14. A radiationsensitive material comprising: a copolymer expressed by a generalformula

 (where X₁ and X₂ represent —C(CH₃)₂R₂,

 Y represents alicyclic group; R₁ represent CH₃ or H; and R₂ representsalkyl group); and a substance generating an acid by application ofradiation. 15-52. (canceled)
 53. A method for forming a patterncomprising the steps of: preparing a resist of a radiation sensitivematerial according to claim 13; applying the resist to a substrate to beprocessed; prebaking the substrate and then selectively exposing theresist on the substrate to radiation; and postbaking the substrate, andthen developing the resist on the substrate to form the pattern.
 54. Amethod for forming a pattern comprising the steps of: preparing a resistof a radiation sensitive material according to claim 14; applying theresist to a substrate to be processed; prebaking the substrate and thenselectively exposing the resist on the substrate to radiation; andpostbaking the substrate, and then developing the resist on thesubstrate to form the pattern. 55-71. (canceled)